Both son and father were home safe Monday after spending four hours the night before at UMass Memorial Medical Center — University Campus in Worcester. They were treated for hypothermia.

The two were riding on the lake when they crashed through the ice and plunged into the frigid waters about 50 feet from shore.

Fighting to keep above water, the father and son reached out to the ice in front of them to no avail.

“I just wanted to keep him alive. I just held onto him as tight as I could,” Mr. Vento said. “Every time we tried to climb up on the ice it broke.”

The father and son had joined other ice fishermen and riders on the ice Sunday evening. They planned to take a quick ride on their snowmobile before the Super Bowl.

Within five minutes the ride morphed from an enjoyable time on the snowmobile into a harrowing ordeal.

While snowmobiling, Mr. Vento saw water bubbling from an old fishing hole about 50 feet from the shoreline. A veteran of more than a decade of snowmobiling, Mr. Vento tried to cut the wheel away from the hole. It was too late; the ice gave way.

“It didn't even crack. It just gave out,” he said.

Grafton police received a 911 call about 5:30 p.m. from Jessica Zaleski reporting that a snowmobile had gone through the ice on Lake Ripple behind Bernard Road, Grafton police said in a news release.

Mrs. Zaleski flagged down Officer Daniel Wenc near the scene and showed him where the accident occurred. Her husband, Roger Zaleski, was out on the ice trying to reach the Ventos.

Mrs. Zaleski told the officer she had heard a snowmobile driving on the ice, then stop. The Zaleskis checked the ice and saw the two riders had gone through.

Office Wenc grabbed a life ring buoy and rope. He saw the father and son.

“Both were struggling to stay afloat and get out of the ice,” police said.

Mr. Zaleski was about half-way to father and son. Officer Wenc joined him on the ice and threw the life ring buoy to the Ventos. Grafton Deputy Fire Chief Michael Mills and Firefighter Brett Mills showed up to assist.

The Ventos grabbed the buoy and the officer, deputy fire chief and firefighter began to pull them to safety.

They were able to pull Colby out, but not Mr. Vento. But Firefighter Mills and others found a canoe and used it to extract Mr. Vento.

Mr. Vento was spent.

“I had no strength to kick and stay above water,” he said. “I was shaking so bad.”

The father and son had been in the water for 10 minutes.

“They (police and fire officials) were running, trying everything they could to help us,” Mr. Vento said. “If they hadn't shown up when they did ...”

He lauded the Zaleskis for hearing their screams and calling for police.

The 1993 snowmobile, which Mr. Vento had just restored, was at the bottom of the lake, under 8 to 9 feet of water.

Mr. Vento was not able to get the snowmobile out of the lake Monday but plans to do so in the spring, according to his wife, Jennifer Vento.

At the hospital Sunday, Colby just wanted to see his father.

“We're doing good. We're still a little shaken up,” Mr. Vento said. “We're just glad we got out alive. He knows I was there to protect him.”